Re: [PATCH 2/2] libata: avoid waking disk to check power

[Aaron Lu <aaron.lu@intel.com>]

+linux-ide

On 11/05/2013 08:53 AM, Phillip Susi wrote:
> When a disk is in SLEEP mode it can not respond to commands,
> including the CHECK POWER command.  Instead of waking up the
> sleeping disk, fake the reply to the CHECK POWER command to
> indicate the disk is in standby mode.  This prevents udisks
> from waking up sleeping disks when it polls to see if they
> are awake or not before trying to read their smart status.

If the disk entered sleep mode due to runtime PM, then udisks can easily
tell by checking the device's runtime status and not send out the query.

But if the disk entered sleep mode due to other reason, the patch may be
necessary. So what's your scenario?

Best regards,
Aaron

> 
> Signed-off-by: Phillip Susi <psusi@ubuntu.com>
> ---
>  drivers/ata/libata-core.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
> index 83b1a9f..573d151 100644
> --- a/drivers/ata/libata-core.c
> +++ b/drivers/ata/libata-core.c
> @@ -5084,6 +5084,13 @@ void ata_qc_issue(struct ata_queued_cmd *qc)
>  
>  	/* if device is sleeping, schedule reset and abort the link */
>  	if (unlikely(qc->dev->flags & ATA_DFLAG_SLEEPING)) {
> +		if (unlikely(qc->tf.command == ATA_CMD_CHK_POWER))
> +		{
> +			/* fake reply to avoid waking drive */
> +			qc->result_tf.nsect = 0;
> +			ata_qc_complete(qc);
> +			return;
> +		}
>  		link->eh_info.action |= ATA_EH_RESET;
>  		ata_ehi_push_desc(&link->eh_info, "waking up from sleep");
>  		ata_link_abort(link);
>